The present invention relates to a mold clamping unit and, more particularly, a mold clamping unit for precision injection molding machine which has a small motion stroke of a movable platen and which is applied to molding of an optical disc such as at a compact disc or digital video disc.
In the precision injection molding machine of this kind, a movable platen (die plate) which holds a movable mold is caused to advance to a stationary platen (die plate) which holds a stationary mold, then a mold is closed and clamped, then a nozzle is caused to touch the mold, then melted resin is injected to the mold cavity, and then the injection side of the molding machine is retreated and the clamping side of the molding machine is opened to take out molded articles. A stamper is attached to the stationary mold and/or the movable mold when an optical disc is molded.
In the prior art, if there is necessity of effecting exchange and/or maintenance operation of the stamper, these operations are executed while the mold is poen.
However, in the mold clamping unit for the precision injection molding machine in the prior art, with taking account of extension of the whole length of the molding machine if a motion stroke of the movable platen is made long, in most cases the motion stroke of the movable platen is set to a minimum value required for molding. Therefore, a gap between the movable platen and the stationary platen in a mold opening state is not sufficient to carry out exchange and maintenance operation of the stamper. Consequently, there has been such a drawback that these operation become troublesome to thus take much time and labor.